High viscosity base stock compositions

ABSTRACT

Methods are provided for producing Group I base stocks having high viscosity and also having one or more properties indicative of a high quality base stock. The resulting Group I base stocks can have a viscosity at 100° C. and/or a viscosity at 40° C. that is greater than the corresponding viscosity for a conventional Group I bright stock formed by solvent processing. Additionally, the resulting Group I base stocks can have one or more properties that are indicative of a high quality base stock.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/254,753 filed Nov. 13, 2015, which is herein incorporated byreference in its entirety. This application is related to two otherco-pending U.S. applications, filed on even date herewith, andidentified by the following Attorney Docket numbers and titles:2015EM335-US2 entitled “High Viscosity Base Stock Compositions” and2015EM336-US2 entitled “High Viscosity Base Stock Compositions”. Theseco-pending U.S. applications are hereby incorporated by reference hereinin their entirety.

FIELD

High viscosity lubricant base stock compositions, methods for makingsuch base stock compositions, and lubricants incorporating such basestock compositions are provided.

BACKGROUND

Conventional methods for solvent processing to form Group I base stockscan produce various types of high viscosity base stocks, such as brightstocks. However, solvent processing is generally less effective atreducing the sulfur and/or nitrogen content of a feed, which can resultin base stocks with detrimental amounts of heteroatom content.Hydrotreating and/or hydrocracking processes can be used prior to and/orafter solvent processing for heteroatom removal, but suchhydroprocessing can significantly reduce the viscosity of the resultinghydrotreated base stock.

More generally, high viscosity base stock capacity has declined asrefiners have transitioned from solvent processing for lubricant basestock production to catalytic processing. While catalytic processing issuitable for making lower viscosity base stocks, the hydrotreating andhydrocracking processes used during catalytic processing tend to limitthe ability to make base stocks with viscosities greater than about 10cSt at 100° C.

Other options for high viscosity base stocks can include specialtypolymeric materials, such as the poly-alpha-olefins in ExxonMobilSpectraSyn™ base stocks. Such polymeric base stocks can have brightstock type viscosities with reduced or minimized sulfur contents.However, production of such polymeric base stocks can be costly due to aneed for specialized feeds to form the desired polymer.

U.S. Pat. No. 4,931,197 describes copolymers formed from α,β-unsaturateddicarboxylic acid esters and α-olefins. The copolymers are produced bycopolymerization in the presence of a peroxide catalyst at temperaturesof 80° C.-210° C. The copolymers are described as suitable for use as alubricant for the shaping treatment of thermoplastic plastics.

U.S. Pat. No. 4,913,794 describes a process configuration for producinghigh viscosity lubricating oils. A lubricating oil and an organicperoxide are co-injected into a reactor to form a higher molecularweight product. The Examples provided in U.S. Pat. No. 4,913,794describe processes using 10 wt % of an organic peroxide in theco-injected feed.

SUMMARY

In an aspect, a base stock composition is provided, the base stockcomposition having a number average molecular weight (M_(n)) of 600g/mol to 3000 g/mol, a weight average molecular weight (M_(w)) of 900g/mol to 10000 g/mol, a polydispersity (M_(w)/M_(n)) of at least 1.4, apour point of 0° C. or less, a viscosity at 100° C. of at least 35 cSt,a viscosity at 40° C. of at least 600 cSt, and a viscosity index of atleast 50.

In another aspect, a method of forming a base stock composition isprovided, the method comprising introducing a feedstock having aviscosity index of 50 to 120, a viscosity at 100° C. of 12 cSt or less,and at least one of a sulfur content greater than 0.03 wt % and anaromatics content greater than 10 wt %, into a coupling reaction stageunder effective coupling conditions to form a coupled effluent; andfractionating at least a portion of the coupled effluent to form atleast a first product fraction having a viscosity index of at least 50,a polydispersity (M_(w)/M_(n)) of at least 1.4, a viscosity at 100° C.of at least 35 cSt, a viscosity at 40° C. of at least 600 cSt, and apour point of 0° C. or less.

In another aspect, a method of forming a base stock composition isprovided, the method comprising introducing a feedstock having aviscosity index of 50 to 120, a viscosity at 100° C. of 12 cSt or less,and at least one of a sulfur content greater than 0.03 wt % and anaromatics content greater than 10 wt %, into a coupling reaction stageunder effective coupling conditions to form a coupled effluent;fractionating at least a portion of the coupled effluent to form atleast a first coupled effluent fraction; and exposing at least a portionof the first coupled effluent fraction to a catalyst under effectivecatalytic processing conditions to form the first product fractionhaving a viscosity index of at least 50, a polydispersity (M_(w)/M_(n))of at least 1.4, a viscosity at 100° C. of at least 35 cSt, a viscosityat 40° C. of at least 600 cSt, and a pour point of 0° C. or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example of a coupling reaction using aperoxide catalyst.

FIG. 2 schematically shows an example of a coupling reaction using aperoxide catalyst.

FIG. 3 schematically shows an example of a coupling reaction in anacidic reaction environment.

FIG. 4 schematically shows an example of a coupling reaction in anacidic reaction environment.

FIG. 5 schematically shows an example of a coupling reaction in thepresence of a solid acid catalyst.

FIG. 6 schematically shows an example of a coupling reaction based onolefin oligomerization.

FIG. 7 schematically shows an example of a reaction system suitable formaking a high viscosity composition as described herein.

FIG. 8 shows Gel Permeation Chromatography results for various basestock samples.

FIG. 9 shows characterization data for various base stock samples.

FIG. 10 shows UV absorptivity data for various base stock samples.

FIG. 11 shows Brookfield viscosity data for lubricants formulated usingvarious base stocks.

FIG. 12 shows oxidation induced changes in kinematic viscosity forlubricants formulated using various base stocks.

FIG. 13 shows Brookfield viscosity data for lubricants formulated usingvarious base stocks.

FIG. 14 shows RPVOT data for lubricants formulated using various basestocks.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art.

Overview

In various aspects, methods are provided for producing Group I basestocks having high viscosity and also having one or more propertiesindicative of a high quality base stock. The resulting Group I basestocks can have a viscosity at 100° C. and/or a viscosity at 40° C. thatis greater than the corresponding viscosity for a conventional Group Ibright stock formed by solvent processing. Additionally, the resultingGroup I base stocks can have one or more of the following propertiesthat are indicative of a high quality base stock: a sulfur content of0.5 wt % or less; a viscosity index of at least 100; a polydispersity ofat least 1.4, or at least 1.7; a crystallization temperature of lessthan −20° C.; and/or other properties.

The high viscosity Group I base stock compositions described herein canbe formed by coupling of compounds from a Group I base stock feed, oroptionally a non-standard Group I base stock type feed. In thisdiscussion, coupling of compounds is defined to include alkylation,oligomerization, and/or other reactions for combining and/or couplingmolecules to increase molecular weight. It has been unexpectedlydiscovered that high molecular weight compositions having a desirablemix of properties can be formed by coupling components from aconventional base stock feed. The resulting compositions can have manyof the benefits of a high molecular weight composition while alsoretaining many of the desirable properties of a conventional lowmolecular weight Group I base stock. Because the composition is formedfrom coupling of compounds from a lower viscosity conventional Group Ibase stock, the initial feed can be hydroprocessed to provide adesirable sulfur, nitrogen, and/or aromatics content prior to couplingto form the high viscosity bright stock. Although such hydroprocessingwill typically reduce the viscosity of a base stock, the coupling of thebase stock to form higher molecular weight compounds results in asubstantially increased viscosity. As a result, any viscosity loss dueto hydroprocessing is reduced, minimized, and/or mitigated.

According to API's classification, Group I base stocks are defined asbase stocks with less than 90 wt % saturated molecules and/or at least0.03 wt % sulfur content. Group I base stocks also have a viscosityindex (VI) of at least 80 but less than 120. Group II base stockscontain at least 90 wt % saturated molecules and less than 0.03 wt %sulfur. Group II base stocks also have a viscosity index of at least 80but less than 120. Group III base stocks contain at least 90 wt %saturated molecules and less than 0.03 wt % sulfur, with a viscosityindex of at least 120.

In this discussion, a stage can correspond to a single reactor or aplurality of reactors. Optionally, multiple parallel reactors can beused to perform one or more of the processes, or multiple parallelreactors can be used for all processes in a stage. Each stage and/orreactor can include one or more catalyst beds containing hydroprocessingcatalyst.

One way of defining a feedstock is based on the boiling range of thefeed. One option for defining a boiling range is to use an initialboiling point for a feed and/or a final boiling point for a feed.Another option, which in some instances may provide a morerepresentative description of a feed, is to characterize a feed based onthe amount of the feed that boils at one or more temperatures. Forexample, a “T5” boiling point or distillation point for a feed isdefined as the temperature at which 5 wt % of the feed is distilled orboiled off. Similarly, a “T95” boiling point is a temperature at which95 wt % of the feed is distilled or boiled off.

In this discussion, unless otherwise specified the lubricant productfraction of a catalytically and/or solvent processed feedstockcorresponds to the fraction having an initial boiling point and/or a T5distillation point of at least about 370° C. (700° F.). A distillatefuel product fraction, such as a diesel product fraction, corresponds toa product fraction having a boiling range from about 177° C. (350° F.)to about 370° C. (700° F.). Thus, distillate fuel product fractions haveinitial boiling points (or alternatively T5 boiling points) of at leastabout 193° C. and final boiling points (or alternatively T95 boilingpoints) of about 370° C. or less. A naphtha fuel product fractioncorresponds to a product fraction having a boiling range from about 35°C. (95° F.) to about 177° C. (350° F.). Thus, naphtha fuel productfractions have initial boiling points (or alternatively T5 boilingpoints) of at least about 35° C. and final boiling points (oralternatively T95 boiling points) of about 177° C. or less. It is notedthat 35° C. roughly corresponds to a boiling point for the variousisomers of a C5 alkane. When determining a boiling point or a boilingrange for a feed or product fraction, an appropriate ASTM test methodcan be used, such as the procedures described in ASTM D2887 or D86.

Feedstock for Forming High Viscosity Base Stock—Group I Base Stock

The base stock compositions described herein can be formed from avariety of feedstocks. A convenient type of feed can be a Group I basestock formed by conventional solvent processing. Optionally, such a feedcan be hydroprocessed to achieve a desired sulfur content, nitrogencontent, and/or aromatics content. In some aspects, the feed cancorrespond to a “viscosity index expanded” Group I base stock. An“viscosity index expanded” Group I base stock is defined herein as afeed that has properties similar to a Group I base stock, but where theviscosity index for the feed is below the typical range for a Group Ibase stock. A viscosity index expanded Group I base stock as definedherein can have a viscosity index of at least 50.

A suitable Group I base stock (and/or expanded viscosity index Group Ibase stock) for forming a high viscosity base stock as described hereincan be characterized in a variety of ways. For example, a suitable GroupI base stock for use as a feed for forming a high viscosity base stockcan have a viscosity at 100° C. of cSt2 cSt to 50 cSt, or 2 cSt to 40cSt, or 2 cSt to 30 cSt, or 2 cSt to 20 cSt, or 2 cSt to 16 cSt, or 2cSt to 12 cSt, or 2 cSt to 10 cSt, or 2 cSt to 8 cSt, or 4 cSt to 50cSt, or 4 cSt to 40 cSt, or 4 cSt to 30 cSt, or 4 cSt to 20 cSt, or 4cSt to 16 cSt, or 4 cSt to 12 cSt, or 4 cSt to 10 cSt, or 4 cSt to 8cSt, or 6 cSt to 50 cSt, or 6 cSt to 40 cSt, or 6 cSt to 30 cSt, or 6cSt to 20 cSt, or 6 cSt to 16 cSt, or 6 cSt to 12 cSt, or 6 cSt to 10cSt, or 8 cSt to 50 cSt, or 8 cSt to 40 cSt, or 8 cSt to 30 cSt, or 8cSt to 20 cSt, or 8 cSt to 16 cSt, or 8 cSt to 12 cSt, or 10 cSt to 50cSt, or 10 cSt to 40 cSt, or 10 cSt to 30 cSt, or 10 cSt to 20 cSt, or10 cSt to 16 cSt, or 12 cSt to 50 cSt, or 12 cSt to 40 cSt, or 12 cSt to30 cSt, or 12 cSt to 20 cSt.

Additionally or alternately, the feedstock can have a viscosity index of50 to 120, or 60 to 120, or 70 to 120, or 80 to 120, or 90 to 120, or100 to 120, or 50 to 110, or 60 to 110, or 70 to 110, or 80 to 110, or90 to 110, or 50 to 100, or 60 to 100, or 70 to 100, or 80 to 100, or 50to 90, or 60 to 90, or 70 to 90, or 50 to 80, or 60 to 80. It is notedthat some of the above listed viscosity index ranges include viscosityindex values that are outside (below) the definition for a Group I basestock, and therefore at least partially correspond to expanded viscosityindex Group I base stocks. In some aspects, at least 50 wt % of thefeedstock, or at least 60 wt %, or at least 70 wt %, or at least 80 wt%, or at least 90 wt %, or substantially all of the feedstock (at least95 wt %) can correspond to a Group I base stock having a viscosity indexwithin the conventional range of viscosity index values for a Group Ibase stock, such as at least 80 and/or 120 or less. Optionally, thefeedstock can include some Group II base stock and/or Group III basestock, such as at least 1 wt %, or at least 5 wt %, or at least 10 wt %,or at least 20 wt %, or at least 30 wt %, and/or less than 50 wt %, or40 wt % or less, or 30 wt % or less, or 20 wt % or less, or 10 wt % orless. Each of the above lower bounds for an amount of Group II and/orGroup III basestock in the feedstock is explicitly contemplated inconjunction with each of the above lower bounds.

Additionally or alternately, the feedstock can have a density at 15.6°C. of 0.92 g/cm3 or less, or 0.91 g/cm3 or less, or 0.90 g/cm3 or less,or 0.89 g/cm3, such as down to about 0.85 g/cm3 or lower.

Additionally or alternately, the molecular weight of the feedstock canbe characterized based on number average molecular weight (correspondingto the typical average weight calculation), and/or based on mass orweight average molecular weight, where the sum of the squares of themolecular weights is divided by the sum of the molecular weights, and/orbased on polydispersity, which is the weight average molecular weightdivided by the number average molecular weight.

The number average molecular weight Mn of a feed can be mathematicallyexpressed as

$\begin{matrix}{M_{n} = \frac{\Sigma_{i}N_{i}M_{i}}{\Sigma_{i}N_{i}}} & (1)\end{matrix}$

In Equation (1), Ni is the number of molecules having a molecular weightMi. The weight average molecular weight, Mw, gives a larger weighting toheavier molecules. The weight average molecular weight can bemathematically expressed as

$\begin{matrix}{M_{w} = \frac{\Sigma_{i}N_{i}M_{i}^{2}}{\Sigma_{i}N_{i}M_{i}}} & (2)\end{matrix}$

The polydispersity can then be expressed as Mw/Mn. In various aspects,the feedstock can have a polydispersity of 1.30 or less, or 1.25 orless, or 1.20 or less, and/or at least about 1.0. Additionally oralternately, the feedstock can have a number average molecular weight(Mn) of 400 to 1200 g/mol. Additionally or alternately, the feedstockcan have a weight average molecular weight (Mw) of 800 to 1400 g/mol.

As an example of a processing for forming a conventional Group I basestock, a feedstock for lubricant base oil production can be processedeither using solvent dewaxing or using catalytic dewaxing. For example,in a lube solvent plant, a vacuum gas oil (VGO) or another suitable feedis fractionated into light neutral (LN) and heavy neutral (HN)distillates and a bottom fraction by some type of vacuum distillation.The bottoms fraction is subsequently deasphalted to recover an asphaltfraction and a brightstock. The LN distillate, HN distillate, andbrightstock are then solvent extracted to remove the most polarmolecules as an extract and corresponding LN distillate, HN distillate,and brighstock raffinates. The raffinates are then solvent dewaxed toobtain a LN distillate, HN distillate, and brightstock basestocks withacceptable low temperature properties. It is beneficial to hydrofinishthe lubricant basestocks either before or after the solvent dewaxingstep. The resulting lubricant basestocks may contain a significantamount of aromatics (up to 25%) and high sulfur (>300 ppm). Thus, thetypical base oils formed from solvent dewaxing alone are Group Ibasestocks. As an alternative, a raffinate hydroconversion step can beperformed prior to the solvent dewaxing. The hydroconversion isessentially a treatment under high H2 pressure in presence of a metalsulfide based hydroprocessing catalyst which remove most of the sulfurand nitrogen. The amount of conversion in the hydroconversion reactionis typically tuned to obtain a predetermined increase in viscosity indexand 95%+saturates. This allows the solvent dewaxed lubricant basestockproducts to be used as Group II or Group II+basestocks. Optionally, thewax recovered from a solvent dewaxing unit may also be processed bycatalytic dewaxing to produce Group III or Group III+lubricantbasestocks.

A wide range of petroleum and chemical feedstocks can be distilled,solvent processed, and/or hydroprocessed in order to form a suitableGroup I base stock for use as a starting material for forming a highviscosity base stock. Suitable feedstocks for solvent processing includewhole and reduced petroleum crudes, atmospheric residua, propanedeasphalted residua, cycle oils, gas oils, including vacuum gas oils andcoker gas oils, light to heavy distillates including raw virgindistillates, hydrocrackates, hydrotreated oils, slack waxes,Fischer-Tropsch waxes, raffinates, and mixtures of these materials.Optionally, feeds derived from a biological source that have anappropriate boiling range can also form at least a portion of thefeedstock.

Typical feeds include, for example, feeds with an initial boiling pointof at least about 650° F. (343° C.), or at least about 700° F. (371°C.), or at least about 750° F. (399° C.). Alternatively, a feed may becharacterized using a T5 boiling point, such as a feed with a T5 boilingpoint of at least about 650° F. (343° C.), or at least about 700° F.(371° C.), or at least about 750° F. (399° C.). In some aspects, thefinal boiling point of the feed can be at least about 1100° F. (593°C.), such as at least about 1150° F. (621° C.) or at least about 1200°F. (649° C.). In other aspects, a feed may be used that does not includea large portion of molecules that would traditional be considered asvacuum distillation bottoms. For example, the feed may correspond to avacuum gas oil feed that has already been separated from a traditionalvacuum bottoms portion. Such feeds include, for example, feeds with afinal boiling point of about 1100° F. (593° C.), or about 1000° F. (538°C.) or less, or about 900° F. (482° C.) or less. Alternatively, a feedmay be characterized using a T95 boiling point, such as a feed with aT95 boiling point of about 1100° F. (593° C.) or less, or about 1000° F.(538° C.) or less, or about 900° F. (482° C.) or less. An example of asuitable type of feedstock is a wide cut vacuum gas oil (VGO) feed, witha T5 boiling point of at least about 700° F. (371° C.) and a T95 boilingpoint of about 1100° F. or less. Optionally, the initial boiling pointof such a wide cut VGO feed can be at least about 700° F. and/or thefinal boiling point can be at least about 1100° F. It is noted thatfeeds with still lower initial boiling points and/or T5 boiling pointsmay also be suitable, so long as sufficient higher boiling material isavailable so that the overall nature of the process is suitable forproduction of lubricant base stocks.

The above feed description corresponds to a potential feed for producinglubricant base stocks. In some aspects, lubricant base stocks can beproduced as part of a process for producing both fuels and lubricants.Because fuels are a desired product in such processes, feedstocks withlower boiling components may also be suitable. For example, a feedstocksuitable for fuels production, such as a light cycle oil, can have a T5boiling point of at least about 350° F. (177° C.), such as at leastabout 400° F. (204° C.). Examples of a suitable boiling range include aboiling range of from about 350° F. (177° C.) to about 700° F. (371°C.), such as from about 390° F. (200° C.) to about 650° F. (343° C.).Thus, a portion of the feed used for fuels and lubricant base stockproduction can include components having a boiling range from about 170°C. to about 350° C. Such components can be part of an initial feed, or afirst feed with a T5 boiling point of about 650° F. (343° C.) can becombined with a second feed, such as a light cycle oil, that includescomponents that boil between 200° C. and 350° C.

An initial feed for lubricant base stock production (or for productionof both fuels and lubricant base stocks) can be distilled to formvarious fractions. For conventional Group I lubricant production,suitable fractions can include vacuum gas oil fractions, deasphalted oilfractions, and combinations thereof.

One fraction formed during vacuum distillation of a feedstock is avacuum gas oil fraction, which corresponds to a distillate fractionhaving a boiling range (as described above) from at least about 650° F.(343° C.) or at least about 700° F. (371° C.) to about 1100° F. (593°C.) or less, or about 1000° F. (538° C.) or less, or about 900° F. (482°C.) or less. A vacuum gas oil fraction can be suitable for solventprocessing to form a Group I base stock. Optionally, a narrower vacuumgas oil cut may be used, such as a narrower cut having an initialboiling point and/or T5 boiling point of at least about 750° F. (399°C.), or at least about 800° F. (427° C.), or at least about 850° F.(454° C.).

Another fraction formed during vacuum distillation of the feedstock is abottoms portion. This bottoms portion can include a variety of types ofmolecules, including asphaltenes. Solvent deasphalting can be used toseparate asphaltenes from the remainder of the bottoms portion. Thisresults in an asphalt or asphaltene fraction and a deasphalted bottomsfraction, which may be suitable for use in production of Group I basestocks.

Solvent deasphalting is a solvent extraction process. Typical solventsinclude alkanes or other hydrocarbons containing about 3 to about 6carbons per molecule. Examples of suitable solvents include propane,n-butane, isobutene, and n-pentane. Alternatively, other types ofsolvents may also be suitable, such as supercritical fluids. Duringsolvent deasphalting, a feed portion is mixed with the solvent. Portionsof the feed that are soluble in the solvent are then extracted, leavingbehind a residue with little or no solubility in the solvent. Typicalsolvent deasphalting conditions include mixing a feedstock fraction witha solvent in a weight ratio of from about 1:2 to about 1:10, such asabout 1:8 or less. Typical solvent deasphalting temperatures range fromabout 40° C. to about 150° C. The pressure during solvent deasphaltingcan be from about 50 psig (345 kPag) to about 500 psig (3447 kPag).

The portion of the deasphalted feedstock that is extracted with thesolvent is often referred to as deasphalted oil. In various aspects, thebottoms from vacuum distillation can be used as the feed to the solventdeasphalter, so the portion extracted with the solvent can also bereferred to as deasphalted bottoms. The yield of deasphalted oil from asolvent deasphalting process varies depending on a variety of factors,including the nature of the feedstock, the type of solvent, and thesolvent extraction conditions. A lighter molecular weight solvent suchas propane will result in a lower yield of deasphalted oil as comparedto n-pentane, as fewer components of a bottoms fraction will be solublein the shorter chain alkane. However, the deasphalted oil resulting frompropane deasphalting is typically of higher quality, resulting inexpanded options for use of the deasphalted oil. Under typicaldeasphalting conditions, increasing the temperature will also usuallyreduce the yield while increasing the quality of the resultingdeasphalted oil. In various embodiments, the yield of deasphalted oilfrom solvent deasphalting can be about 85 wt % or less of the feed tothe deasphalting process, or about 75 wt % or less. Preferably, thesolvent deasphalting conditions are selected so that the yield ofdeasphalted oil is at least about 65 wt %, such as at least about 70 wt% or at least about 75 wt %. The deasphalted bottoms resulting from thesolvent deasphalting procedure are then combined with the higher boilingportion from the vacuum distillation unit for solvent processing.

After a deasphalting process, the yield of deasphalting residue istypically at least about 15 wt % of the feed to the deasphaltingprocess, but is preferably about 35 wt % or less, such as about 30 wt %or less or 25 wt % or less. The deasphalting residue can be used, forexample, for making various grades of asphalt.

Two types of solvent processing can be performed on vacuum gas oiland/or deasphalted bottoms as part of production of a Group I basestock. The first type of solvent processing is a solvent extraction toreduce the aromatics content and/or the amount of polar molecules. Thesolvent extraction process selectively dissolves aromatic components toform an aromatics-rich extract phase while leaving the more paraffiniccomponents in an aromatics-poor raffinate phase. Naphthenes aredistributed between the extract and raffinate phases. Typical solventsfor solvent extraction include phenol, furfural and N-methylpyrrolidone. By controlling the solvent to oil ratio, extractiontemperature and method of contacting distillate to be extracted withsolvent, one can control the degree of separation between the extractand raffinate phases. Any convenient type of liquid-liquid extractor canbe used, such as a counter-current liquid-liquid extractor. Depending onthe initial concentration of aromatics in the deasphalted bottoms, theraffinate phase can have an aromatics content of about 5 wt % to about25 wt %. For typical feeds, the aromatics contents will be at leastabout 10 wt %.

In some aspects, a deasphalted bottoms fraction and a vacuum gas oilfraction can be solvent processed together. Alternatively, differentfractions can be solvent processed separately, to facilitate formationof different types of lubricant base oils. For example, a vacuum gas oilfraction can be solvent extracted and then solvent dewaxed to form aGroup I base oil of lower viscosity while a deasphalted bottoms fractioncan be solvent processed to form a conventional brightstock. Of course,multiple vacuum gas oil fractions and/or deasphalted oil fractions couldbe solvent processed separately if more than one distinct Group I baseoil and/or brightstock is desired.

The raffinate from the solvent extraction is optionally but preferablyunder-extracted. In such optional aspects, the extraction is carried outunder conditions such that the raffinate yield is increased or maximizedwhile still removing most of the lowest quality molecules from the feed.Raffinate yield may be increased or maximized by controlling extractionconditions, for example, by lowering the solvent to oil treat ratioand/or decreasing the extraction temperature. The raffinate from thesolvent extraction unit can then be solvent dewaxed under solventdewaxing conditions to remove hard waxes from the raffinate.

Solvent dewaxing typically involves mixing the raffinate feed from thesolvent extraction unit with chilled dewaxing solvent to form anoil-solvent solution. Precipitated wax is thereafter separated by, forexample, filtration. The temperature and solvent are selected so thatthe oil is dissolved by the chilled solvent while the wax isprecipitated.

An example of a suitable solvent dewaxing process involves the use of acooling tower where solvent is prechilled and added incrementally atseveral points along the height of the cooling tower. The oil-solventmixture is agitated during the chilling step to permit substantiallyinstantaneous mixing of the prechilled solvent with the oil. Theprechilled solvent is added incrementally along the length of thecooling tower so as to maintain an average chilling rate at or below 10°F. per minute, usually between about 1 to about 5° F. per minute. Thefinal temperature of the oil-solvent/precipitated wax mixture in thecooling tower will usually be between 0 and 50° F. (−17.8 to 10° C.).The mixture may then be sent to a scraped surface chiller to separateprecipitated wax from the mixture.

Representative dewaxing solvents are aliphatic ketones having 3-6 carbonatoms such as methyl ethyl ketone and methyl isobutyl ketone, lowmolecular weight hydrocarbons such as propane and butane, and mixturesthereof. The solvents may be mixed with other solvents such as benzene,toluene or xylene.

In general, the amount of solvent added will be sufficient to provide aliquid/solid weight ratio between the range of 5/1 and 20/1 at thedewaxing temperature and a solvent/oil volume ratio between 1.5/1 to5/1. The solvent dewaxed oil is typically dewaxed to an intermediatepour point, preferably less than about +10° C., such as less than about5° C. or less than about 0° C. The resulting solvent dewaxed base stockcan be suitable for use in forming one or more types of Group I baseoils. The aromatics content will typically be greater than 10 wt % inthe solvent dewaxed oil. Additionally, the sulfur content of the solventdewaxed oil will typically be greater than 300 wppm.

Either prior to or after any of the above solvent processing steps, thefeedstock can also be hydrotreated or otherwise hydroprocessed to reducethe sulfur content of the base stock. Some feeds for conventional GroupI base stock production can have an initial sulfur content at least 1000wppm of sulfur, or at least 2000 wppm, or at least 4000 wppm, or atleast 10,000 wppm, or at least about 20,000 wppm. Hydrprocessing can beused to reduce the sulfur content of the resulting conventional Group Ibase stock to about 1000 wppm or less, or about 500 wppm or less, orabout 100 wppm or less. Optionally but preferably, the hydroprocessingcan also retain at least about 10 wt % aromatics in the resultinghydroprocessed base stock, or at least about 15 wt %, or at least about20 wt %, or at least about 25 wt %, or at least about 30 wt %, such asup to about 50 wt % or up to about 70 wt %.

Group I base stocks can also be formed by catalytic dewaxing of theraffinate from a solvent extraction unit. Suitable dewaxing catalystscan include molecular sieves such as crystalline aluminosilicates(zeolites). Examples of suitable dewaxing catalysts can include, but arenot limited to, ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, zeoliteBeta, or a combination thereof. Catalysts based on ZSM-5 are preferredfor the production of Group I base stocks. In various embodiments, thedewaxing catalysts can optionally further include a metal hydrogenationcomponent. The metal hydrogenation component is typically a Group VIand/or a Group VIII metal. Preferably the metal hydrogenation componentcan be a combination of a non-noble Group VIII metal with a Group VImetal. Suitable combinations can include Ni, Co, or Fe with Mo or W,preferably Ni with Mo or W.

For embodiments where the metal is a combination of a non-noble GroupVIII metal with a Group VI metal, the combined amount of metal can befrom 0.5 wt % to 40 wt %, or 2 wt % to 35 wt %, or 5 wt % to 30 wt %.

The dewaxing catalysts useful in processes according to the disclosurecan also include a binder. The amount of zeolite in a catalystformulated using a binder can be from about 30 wt % zeolite to 90 wt %zeolite relative to the combined weight of binder and zeolite.Preferably, the amount of zeolite is at least about 50 wt % of thecombined weight of zeolite and binder, such as at least about 60 wt % orfrom about 65 wt % to about 80 wt %.

A zeolite can be combined with binder in any convenient manner. Forexample, a bound catalyst can be produced by starting with powders ofboth the zeolite and binder, combining and mulling the powders withadded water to form a mixture, and then extruding the mixture to producea bound catalyst of a desired size. Extrusion aids can also be used tomodify the extrusion flow properties of the zeolite and binder mixture.

Effective dewaxing conditions can include a temperature of at leastabout 500° F. (260° C.), or at least about 550° F. (288° C.), or atleast about 600° F. (316° C.), or at least about 650° F. (343° C.).Alternatively, the temperature can be about 800° F. (427° C.) or less,or 750° F. (399° C.) or less, or about 700° F. (371° C.) or less, orabout 650° F. (343° C.) or less. For example, the dewaxing temperaturecan be about 600° F. (316° C.) to about 750° F. (399° C.), or about 650°F. (343° C.) to about 750° F. (399° C.), or about 650° F. (343° C.) toabout 725° F. (385° C.), or about 650° F. (343° C.) to about 700° F.(371° C.), or about 675° F. (357° C.) to about 750° F. (399° C.), orabout 700° F. (371° C.) to about 750° F. (399° C.). The pressure can beat least about 250 psig (1.8 MPa), or at least about 500 psig (3.4 MPa),or at least about 750 psig (5.2 MPa), or at least about 1000 psig (6.9MPa). Alternatively, the pressure can be about 5000 psig (34.6 MPa) orless, or about 3000 psig (20.7 MPa) or less, or about 1500 psig (10.3MPa) or less, or about 1200 psig (8.2 MPa) or less, or about 1000 psig(6.9 MPa) or less, or about 800 psig (5.5 MPa) or less. The LiquidHourly Space Velocity (LHSV) can be at least about 0.5 hr⁻¹, or at leastabout 1.0 hr⁻¹, or at least about 1.5 hr⁻¹. Alternatively, the LHSV canbe about 10.0 hr⁻¹ or less, or about 5.0 hr⁻¹ or less, or about 3.0 hr⁻¹or less, or about 2.0 hr⁻¹ or less. The treat gas rate can be at leastabout 500 scf/bbl (89 Nm³/m³), at least about 750 scf/bbl (134 Nm³/m³),or at least about 1000 scf/bbl (178 Nm³/m³). Alternatively, the treatgas rate can be about 10000 scf/bbl (1781 Nm³/m³) or less, or about 6000scf/bbl (1069 Nm³/m³) or less, or about 4000 scf/bbl (712 Nm³/m³) orless, or about 2000 scf/bbl (356 Nm³/m³) or less, or about 1500 scf/bbl(267 Nm³/m³) or less.

Reactions to Form High Viscosity Base Stocks

There are various chemistry options that can be used for increasing themolecular weight of components found in Group I base stocks (optionallyincluding expanded viscosity index Group I base stocks). Examples ofsuitable reactions can include, but are not limited to, reactions suchas olefin oligomerization, Friedel-Craft aromatic alkylation, radicalcoupling via peroxide, or catalyzed coupling using sulfur. In general,higher temperature reaction conditions can provide an increased reactionrate, while longer reaction times can improve the yield of coupledreaction product.

FIG. 1 shows an example of the general scheme for coupling compounds viaradical coupling using a peroxide catalyst. The reaction shown in FIG. 1is provided as an example, and is not intended to indicate a particularreaction location or product. As shown in FIG. 1, a compound is exposedto the presence of a peroxide, which results in formation of a radical.The radical compound has an increased reactivity which can facilitatecoupling with another compound. It is noted that although the peroxidemay be referred to as a catalyst herein, the peroxide is convertedduring the reaction from peroxide to two alcohols.

A similar schematic example of a radical coupling reaction withlubricant boiling range molecules is shown in FIG. 2. The reaction shownin FIG. 1 is provided as an example, and is not intended to indicate aparticular reaction location or product. As shown in the examplereaction in FIG. 2, radical coupling using peroxide can be used tocouple two lubricant boiling range molecules together to form a largercompound. It has been discovered that converting a portion of alubricant boiling range feed, such as a Group I lubricant base stock, tohigher molecular weight compounds can produce a high viscosity lubricantbase stock.

In the reaction scheme shown in FIG. 2, a dialkyl peroxide is used asthe source of peroxide. Any convenient dialkyl peroxide can be used.Optionally, the alkyl groups in the peroxide can each include at least 3carbons, or at least 4 carbons, or at least 5 carbons. In some aspects,the peroxide can be bonded to one or both of the alkyl groups at atertiary carbon. For example, one or both of the alkyl groups can be at-butyl (tertiary butyl) group. To facilitate the coupling reaction, afeedstock can be mixed with 5 wt % to 80 wt % (relative to a weight ofthe feedstock) of dialkyl peroxide(s), or 5 wt % to 70 wt %, or 5 wt %to 60 wt %, or 5 wt % to 50 wt %, or 5 wt % to 40 wt %, or 5 wt % to 30wt %, or 5 wt % to 20 wt %, or 10 wt % to 80 wt %, or 10 wt % to 70 wt%, or 10 wt % to 60 wt %, or 10 wt % to 50 wt %, or 10 wt % to 40 wt %,or 10 wt % to 30 wt %, or 10 wt % to 20 wt %, or 15 wt % to 80 wt %, or15 wt % to 70 wt %, or 15 wt % to 60 wt %, or 15 wt % to 50 wt %, or 15wt % to 40 wt %, or 15 wt % to 30 wt %, or 20 wt % to 80 wt %, or 20 wt% to 70 wt %, or 20 wt % to 60 wt %, or 20 wt % to 50 wt %, or 20 wt %to 40 wt %, or 20 wt % to 30 wt %, or 25 wt % to 80 wt %, or 25 wt % to70 wt %, or 25 wt % to 60 wt %, or 25 wt % to 50 wt %, or 25 wt % to 40wt %, or 30 wt % to 80 wt %, or 30 wt % to 70 wt %, or 30 wt % to 60 wt%, or 30 wt % to 50 wt %, or 30 wt % to 40 wt %. The feedstock can beexposed to the dialkyl peroxide for a convenient period of time, such asabout 10 minutes to about 10 hours. The temperature during exposure ofthe feedstock to the dialkyl peroxide can be from about 50° C. to about300° C., preferably from about 120° C. to about 260° C., optionally atleast about 140° C. and/or optionally about 230° C. or less. It is notedthat while the above time and temperature conditions refer to batchoperation, one of skill in the art can readily adapt this reaction as acontinuous flow reaction scheme by selecting appropriate flowrates/residence times/temperatures. The reactor configuration andtemperatures/space velocities described in U.S. Pat. No. 4,913,794provide another example of conditions that can be used for formation ofhigh viscosity, high quality base stocks, which is incorporated hereinby reference with respect to the reactor configuration, temperatures,and space velocities.

FIGS. 3 to 5 show schematic examples of other types of reaction schemes,including examples of aromatic coupling with sulfuric acid (FIG. 3),aromatic coupling with oxalic acid, formaldehyde, or sulfur (FIG. 4),and aromatic alkylation in the presence of a molecular sieve catalystwith a supported (noble) metal (FIG. 5). All of the reactions shown inFIGS. 3-5 are intended as examples, as these reaction mechanisms aregenerally known to those of skill in the art. Coupling using sulfuricacid as shown in FIG. 3 can generally be performed at temperaturesbetween 150° C. and 250° C. and at pressures between about 100 psig (0.7MPag) and 1000 psig (7 MPag). Coupling using sulfur or an organiccompound containing a carbonyl group as shown in FIG. 4 can generally beperformed at temperatures between 100° C. and 200° C. and/or attemperatures suitable for general Friedel-Craft alkylation. Anadditional acid can also be introduced into the reaction environment tocatalyze the reaction. Suitable acids can include, for example,conventional catalysts suitable for Friedel-Craft alkylation. Aromaticalkylation in the presence of a molecular sieve with a supported metalis also a conventionally known process. FIG. 5 shows an example ofaromatic alkylation performed in the presence of a Pt on MCM-22catalyst, but any convenient conventional aromatic alkylation catalystcan be used.

It is noted that all of the reaction mechanisms shown in FIGS. 1-5involve elevated temperature and the presence of a peroxide catalyst, anacidic catalyst, and/or an acidic reaction environment. An additionalreaction that can also occur under conditions similar to those shown inFIGS. 1-5 is olefin oligomerization, where two olefin-containingcompounds within a feed are coupled to form a single largerolefin-containing compound. An example of an olefin oligomerizationreaction is shown in FIG. 6. Optionally, if a feed suitable for Group Ibase stock formation and/or a Group I base stock had a sufficient amountof olefin-containing compounds, olefin oligomerization could be used asthe primary coupling reaction mechanism for forming a high viscositybase stock.

The product formed after exposing a Group I base stock to a couplingreaction can correspond to a high viscosity base stock with desirableproperties, or optionally additional hydroprocessing can be used toimprove the properties of the high viscosity base stock. As an example,in aspects where the coupling reaction is based on a peroxide catalyst,the coupling reaction may introduce additional oxygen heteroatoms intothe reaction product. Prior to hydroprocessing, the properties of thehigh viscosity base stock product may be less favorable due to thepresence of the oxygen heteroatoms. Hydroprocessing of the highviscosity base stock can remove the oxygen heteroatoms, leading toimproved properties.

FIG. 7 shows an example of a reaction system suitable for production ofhigh viscosity base stocks as described herein. In FIG. 7, an initialfeed 705 of Group I base stock (or expanded viscosity index Group I basestock) is passed into a coupling reaction stage 710, such as a reactionstage for coupling in the presence of a peroxide catalyst. The effluent715 from the coupling stage is passed into a fractionator 720, such as avacuum distillation column. The fractionator 720 can allow forseparation of the coupling effluent 715 into a plurality of products,such as one or more light neutral products 732, one or more heavyneutral products 734, and a brightstock product 736. Optionally, aportion of the brightstock product 736 can be used without furthertreatment. The remaining portion 738 of the brightstock product can thenbe catalytically processed 740. Catalytic processing 740 can include oneor more of hydrotreatment, catalytic dewaxing, and/or hydrofinishing.The catalytically processed effluent 745 can then be separated 750 toform at least a fuels boiling range product 752 and a high viscositybase stock product 755. The fuels boiling range product can have a T95boiling point of about 750° F. (399° C.) or less, or about 700° F. (371°C.) or less, or about 650° F. (343° C.) or less. Optionally, a pluralityof fuels boiling range products 752 can be formed, with the additionalfuels boiling range products corresponding to naphtha boiling rangeproducts, kerosene boiling range products, and/or additional lowerboiling range diesel products.

It is noted that some feeds can allow for production of high viscositybase stocks as described herein without passing the coupled effluentthrough a catalytic processing stage 740. For example, a feed comprisinga raffinate hydroconversion effluent can have a sufficiently lowaromatics content to potentially avoid the need for catalytic treatmentof the coupled effluent.

Catalytic Processing Conditions

After the coupling reaction, the high viscosity base stocks describedherein can be optionally but preferably catalytically processed toimprove the properties of the base stock. The optional catalyticprocessing can include one or more of hydrotreatment, catalyticdewaxing, and/or hydrofinishing. In aspects where more than one type ofcatalytic processing is performed, the effluent from a first type ofcatalytic processing can optionally be separated prior to the secondtype of catalytic processing. For example, after a hydrotreatment orhydrofinishing process, a gas-liquid separation can be performed toremove light ends, H₂S, and/or NH₃ that may have formed.

Hydrotreatment is typically used to reduce the sulfur, nitrogen, andaromatic content of a feed. The catalysts used for hydrotreatment of theheavy portion of the crude oil from the flash separator can includeconventional hydroprocessing catalysts, such as those that comprise atleast one Group VIII non-noble metal (Columns 8-10 of IUPAC periodictable), preferably Fe, Co, and/or Ni, such as Co and/or Ni; and at leastone Group VI metal (Column 6 of IUPAC periodic table), preferably Moand/or W. Such hydroprocessing catalysts optionally include transitionmetal sulfides that are impregnated or dispersed on a refractory supportor carrier such as alumina and/or silica. The support or carrier itselftypically has no significant/measurable catalytic activity.Substantially carrier- or support-free catalysts, commonly referred toas bulk catalysts, generally have higher volumetric activities thantheir supported counterparts.

The catalysts can either be in bulk form or in supported form. Inaddition to alumina and/or silica, other suitable support/carriermaterials can include, but are not limited to, zeolites, titania,silica-titania, and titania-alumina. Suitable aluminas are porousaluminas such as gamma or eta having average pore sizes from 50 to 200Å, or 75 to 150 Å; a surface area from 100 to 300 m²/g, or 150 to 250m²/g; and a pore volume of from 0.25 to 1.0 cm³/g, or 0.35 to 0.8 cm³/g.More generally, any convenient size, shape, and/or pore sizedistribution for a catalyst suitable for hydrotreatment of a distillate(including lubricant base oil) boiling range feed in a conventionalmanner may be used. It is within the scope of the present disclosurethat more than one type of hydroprocessing catalyst can be used in oneor multiple reaction vessels.

The at least one Group VIII non-noble metal, in oxide form, cantypically be present in an amount ranging from about 2 wt % to about 40wt %, preferably from about 4 wt % to about 15 wt %. The at least oneGroup VI metal, in oxide form, can typically be present in an amountranging from about 2 wt % to about 70 wt %, preferably for supportedcatalysts from about 6 wt % to about 40 wt % or from about 10 wt % toabout 30 wt %. These weight percents are based on the total weight ofthe catalyst. Suitable metal catalysts include cobalt/molybdenum (1-10%Co as oxide, 10-40% Mo as oxide), nickel/molybdenum (1-10% Ni as oxide,10-40% Co as oxide), or nickel/tungsten (1-10% Ni as oxide, 10-40% W asoxide) on alumina, silica, silica-alumina, or titania.

The hydrotreatment is carried out in the presence of hydrogen. Ahydrogen stream is, therefore, fed or injected into a vessel or reactionzone or hydroprocessing zone in which the hydroprocessing catalyst islocated. Hydrogen, which is contained in a hydrogen “treat gas,” isprovided to the reaction zone. Treat gas, as referred to in thisdisclosure, can be either pure hydrogen or a hydrogen-containing gas,which is a gas stream containing hydrogen in an amount that issufficient for the intended reaction(s), optionally including one ormore other gasses (e.g., nitrogen and light hydrocarbons such asmethane), and which will not adversely interfere with or affect eitherthe reactions or the products. Impurities, such as H₂S and NH₃ areundesirable and would typically be removed from the treat gas before itis conducted to the reactor. The treat gas stream introduced into areaction stage will preferably contain at least about 50 vol. % and morepreferably at least about 75 vol. % hydrogen.

Hydrogen can be supplied at a rate of from about 100 SCF/B (standardcubic feet of hydrogen per barrel of feed) (17 Nm³/m³) to about 1500SCF/B (253 Nm³/m³). Preferably, the hydrogen is provided in a range offrom about 200 SCF/B (34 Nm³/m³) to about 1200 SCF/B (202 Nm³/m³).Hydrogen can be supplied co-currently with the input feed to thehydrotreatment reactor and/or reaction zone or separately via a separategas conduit to the hydrotreatment zone.

Hydrotreating conditions can include temperatures of 200° C. to 450° C.,or 315° C. to 425° C.; pressures of 250 psig (1.8 MPag) to 5000 psig(34.6 MPag) or 300 psig (2.1 MPag) to 3000 psig (20.8 MPag); liquidhourly space velocities (LHSV) of 0.1 hr¹ to 10 hr^(−l); and hydrogentreat rates of 200 scf/B (35.6 m³/m³) to 10,000 scf/B (1781 m³/m³), or500 (89 m³/m³) to 10,000 scf/B (1781 m³/m³).

Additionally or alternately, a potential high viscosity base stock canbe exposed to catalytic dewaxing conditions. Catalytic dewaxing can beused to improve the cold flow properties of a high viscosity base stock,and can potentially also perform some heteroatom removal and aromaticsaturation. Suitable dewaxing catalysts can include molecular sievessuch as crystalline aluminosilicates (zeolites). In an embodiment, themolecular sieve can comprise, consist essentially of, or be ZSM-5,ZSM-22, ZSM-23, ZSM-35, ZSM-48, zeolite Beta, or a combination thereof,for example ZSM-23 and/or ZSM-48, or ZSM-48 and/or zeolite Beta.Optionally but preferably, molecular sieves that are selective fordewaxing by isomerization as opposed to cracking can be used, such asZSM-48, zeolite Beta, ZSM-23, or a combination thereof. Additionally oralternately, the molecular sieve can comprise, consist essentially of,or be a 10-member ring 1-D molecular sieve. Examples include EU-1,ZSM-35 (or ferrierite), ZSM-11, ZSM-57, NU-87, SAPO-11, ZSM-48, ZSM-23,and ZSM-22. Preferred materials are EU-2, EU-11, ZBM-30, ZSM-48, orZSM-23. ZSM-48 is most preferred. Note that a zeolite having the ZSM-23structure with a silica to alumina ratio of from about 20:1 to about40:1 can sometimes be referred to as SSZ-32. Other molecular sieves thatare isostructural with the above materials include Theta-1, NU-10,EU-13, KZ-1, and NU-23. Optionally but preferably, the dewaxing catalystcan include a binder for the molecular sieve, such as alumina, titania,silica, silica-alumina, zirconia, or a combination thereof, for examplealumina and/or titania or silica and/or zirconia and/or titania.

Preferably, the dewaxing catalysts used in processes according to thedisclosure are catalysts with a low ratio of silica to alumina. Forexample, for ZSM-48, the ratio of silica to alumina in the zeolite canbe less than about 200:1, such as less than about 110:1, or less thanabout 100:1, or less than about 90:1, or less than about 75:1. Invarious embodiments, the ratio of silica to alumina can be from 50:1 to200:1, such as 60:1 to 160:1, or 70:1 to 100:1.

In various embodiments, the catalysts according to the disclosurefurther include a metal hydrogenation component. The metal hydrogenationcomponent is typically a Group VI and/or a Group VIII metal. Preferably,the metal hydrogenation component is a Group VIII noble metal.Preferably, the metal hydrogenation component is Pt, Pd, or a mixturethereof. In an alternative preferred embodiment, the metal hydrogenationcomponent can be a combination of a non-noble Group VIII metal with aGroup VI metal. Suitable combinations can include Ni, Co, or Fe with Moor W, preferably Ni with Mo or W.

The metal hydrogenation component may be added to the catalyst in anyconvenient manner. One technique for adding the metal hydrogenationcomponent is by incipient wetness. For example, after combining azeolite and a binder, the combined zeolite and binder can be extrudedinto catalyst particles. These catalyst particles can then be exposed toa solution containing a suitable metal precursor. Alternatively, metalcan be added to the catalyst by ion exchange, where a metal precursor isadded to a mixture of zeolite (or zeolite and binder) prior toextrusion.

The amount of metal in the catalyst can be at least 0.1 wt % based oncatalyst, or at least 0.15 wt %, or at least 0.2 wt %, or at least 0.25wt %, or at least 0.3 wt %, or at least 0.5 wt % based on catalyst. Theamount of metal in the catalyst can be 20 wt % or less based oncatalyst, or 10 wt % or less, or 5 wt % or less, or 2.5 wt % or less, or1 wt % or less. For embodiments where the metal is Pt, Pd, another GroupVIII noble metal, or a combination thereof, the amount of metal can befrom 0.1 to 5 wt %, preferably from 0.1 to 2 wt %, or 0.25 to 1.8 wt %,or 0.4 to 1.5 wt %. For embodiments where the metal is a combination ofa non-noble Group VIII metal with a Group VI metal, the combined amountof metal can be from 0.5 wt % to 20 wt %, or 1 wt % to 15 wt %, or 2.5wt % to 10 wt %.

The dewaxing catalysts can also include a binder. In some embodiments,the dewaxing catalysts can be formulated using a low surface areabinder, where a low surface area binder represents a binder with asurface area of 100 m²/g or less, or 80 m²/g or less, or 70 m²/g orless. The amount of zeolite in a catalyst formulated using a binder canbe from about 30 wt % zeolite to 90 wt % zeolite relative to thecombined weight of binder and zeolite. Preferably, the amount of zeoliteis at least about 50 wt % of the combined weight of zeolite and binder,such as at least about 60 wt % or from about 65 wt % to about 80 wt %.

A zeolite can be combined with binder in any convenient manner. Forexample, a bound catalyst can be produced by starting with powders ofboth the zeolite and binder, combining and mulling the powders withadded water to form a mixture, and then extruding the mixture to producea bound catalyst of a desired size. Extrusion aids can also be used tomodify the extrusion flow properties of the zeolite and binder mixture.The amount of framework alumina in the catalyst may range from 0.1 to3.33 wt %, or 0.1 to 2.7 wt %, or 0.2 to 2 wt %, or 0.3 to 1 wt %.

Process conditions in a catalytic dewaxing zone in a sour environmentcan include a temperature of from 200 to 450° C., preferably 270 to 400°C., a hydrogen partial pressure of from 1.8 MPag to 34.6 MPag (250 psigto 5000 psig), preferably 4.8 MPag to 20.8 MPag, and a hydrogencirculation rate of from 35.6 m³/m³ (200 SCF/B) to 1781 m³/m³ (10,000scf/B), preferably 178 m³/m³ (1000 SCF/B) to 890.6 m³/m³ (5000 SCF/B).In still other embodiments, the conditions can include temperatures inthe range of about 600° F. (343° C.) to about 815° F. (435° C.),hydrogen partial pressures of from about 500 psig to about 3000 psig(3.5 MPag-20.9 MPag), and hydrogen treat gas rates of from about 213m³/m³ to about 1068 m³/m³ (1200 SCF/B to 6000 SCF/B). These latterconditions may be suitable, for example, if the dewaxing stage isoperating under sour conditions. The LHSV can be from about 0.2 h⁻¹ toabout 10 h⁻¹, such as from about 0.5 h¹ to about 5 h⁻¹ and/or from about1 h⁻¹ to about 4 h¹.

Additionally or alternately, a potential high viscosity base stock canbe exposed to hydrofinishing or aromatic saturation conditions.Hydrofinishing and/or aromatic saturation catalysts can includecatalysts containing Group VI metals, Group VIII metals, and mixturesthereof. In an embodiment, preferred metals include at least one metalsulfide having a strong hydrogenation function. In another embodiment,the hydrofinishing catalyst can include a Group VIII noble metal, suchas Pt, Pd, or a combination thereof. The mixture of metals may also bepresent as bulk metal catalysts wherein the amount of metal is about 30wt. % or greater based on catalyst. Suitable metal oxide supportsinclude low acidic oxides such as silica, alumina, silica-aluminas ortitania, preferably alumina. The preferred hydrofinishing catalysts foraromatic saturation will comprise at least one metal having relativelystrong hydrogenation function on a porous support. Typical supportmaterials include amorphous or crystalline oxide materials such asalumina, silica, and silica-alumina. The support materials may also bemodified, such as by halogenation, or in particular fluorination. Themetal content of the catalyst is often as high as about 20 weightpercent for non-noble metals. In an embodiment, a preferredhydrofinishing catalyst can include a crystalline material belonging tothe M41S class or family of catalysts. The M41 S family of catalysts aremesoporous materials having high silica content. Examples includeMCM-41, MCM-48 and MCM-50. A preferred member of this class is MCM-41.If separate catalysts are used for aromatic saturation andhydrofinishing, an aromatic saturation catalyst can be selected based onactivity and/or selectivity for aromatic saturation, while ahydrofinishing catalyst can be selected based on activity for improvingproduct specifications, such as product color and polynuclear aromaticreduction.

Hydrofinishing conditions can include temperatures from about 125° C. toabout 425° C., preferably about 180° C. to about 280° C., a hydrogenpartial pressure from about 500 psig (3.4 MPa) to about 3000 psig (20.7MPa), preferably about 1500 psig (10.3 MPa) to about 2500 psig (17.2MPa), and liquid hourly space velocity from about 0.1 hr⁻¹ to about 5hr⁻¹ LHSV, preferably about 0.5 hr⁻¹ to about 1.5 hr⁻¹. Additionally, ahydrogen treat gas rate of from 35.6 m³/m³ to 1781 m³/m³ (200 SCF/B to10,000 SCF/B) can be used.

Properties of High Viscosity Base Stocks

After exposing a feedstock to coupling reaction conditions, and afterany optional catalytic processing, the resulting effluent can befractionated to form at least a high viscosity base stock product. Thehigh viscosity base stock product can be characterized in a variety ofmanners to demonstrate the novel nature of the composition.

In the examples described herein, the fractionation of the effluent fromthe coupling reaction corresponds to a fractionation to separate theparent feed material (lower molecular weight) from the products from thecoupling reaction. This can be done, for example, using a short pathsingle stage vacuum distillation, or via any other convenient type oftemperature based separator/fractionator. Another fractionation optioncan be to further fractionate the coupled reaction product to createmultiple base stocks, such as making both a heavy neutral and a brightstock range material from the coupled reaction product. Still anotheroption could be to perform a fractionation so that the lightest (i.e.,lowest molecular weight) portions of the couple reaction product areseparated along with the initial feed. This type of narrower cut portionof the coupled reaction product could provide a higher viscosity basestock from the coupled reaction product but at the cost of a yielddebit.

One direct method of characterization of a high viscosity base stock isto use Gel Permeation Chromatography (GPC) to characterize the molecularweight distribution of the high viscosity base stock. GPC is a techniquemore commonly used for characterization of high molecular weightpolymers. However, due to the higher molecular weight distribution of ahigh viscosity base stock as described herein relative to a conventionalbright stock (or other Group I base stock), GPC can be beneficial forillustrating the differences.

Three quantities that can be determined by GPC (or by any otherconvenient mass characterization method) are polydispersity, M_(w), andM_(n), all as defined above.

With regard to a traditional average weight, a high viscosity feedstockcan have a number average molecular weight (M_(n)) of 600 g/mol to 3000g/mol. For example, the number average molecular weight can be 600 g/molto 3000 g/mol, or 600 g/mol to 2500 g/mol, or 600 g/mol to 2000 g/mol,or 700 g/mol to 3000 g/mol, or 700 g/mol to 2500 g/mol, or 700 g/mol to2000 g/mol, or 800 g/mol to 3000 g/mol, or 800 g/mol to 2500 g/mol, or800 g/mol to 2000 g/mol, or 900 g/mol to 3000 g/mol, or 900 g/mol to2500 g/mol, or 900 g/mol to 2000 g/mol, or 1000 g/mol to 3000 g/mol, or1000 g/mol to 2500 g/mol, or 1000 g/mol to 2000 g/mol, or 1100 g/mol to3000 g/mol, or 1100 g/mol to 2500 g/mol, or 1100 g/mol to 2000 g/mol.

Additionally or alternately, a high viscosity feedstock can have aweight average molecular weight (M_(w)) of 900 g/mol to 10000 g/mol. Forexample, the weight average molecular weight can be 900 g/mol to 10000g/mol, or 900 g/mol to 9000 g/mol, or 900 g/mol to 8000 g/mol, or 900g/mol to 7000 g/mol, or 1000 g/mol to 10000 g/mol, or 1000 g/mol to 9000g/mol, or 1000 g/mol to 8000 g/mol, or 1000 g/mol to 7000 g/mol, or 1200g/mol to 10000 g/mol, or 1200 g/mol to 9000 g/mol, or 1200 g/mol to 8000g/mol, or 1200 g/mol to 7000 g/mol, or 1500 g/mol to 10000 g/mol, or1500 g/mol to 9000 g/mol, or 1500 g/mol to 8000 g/mol, or 1500 g/mol to7000 g/mol, or 2000 g/mol to 10000 g/mol, or 2000 g/mol to 9000 g/mol,or 2000 g/mol to 8000 g/mol, or 2000 g/mol to 7000 g/mol.

Additionally or alternately, a high viscosity base stock can have anunexpectedly high polydispersity relative to a base stock formed byconventional solvent and/or catalytic processing. The polydispersity canbe expressed as M_(w)/M_(n). In various aspects, the feedstock can havea polydispersity of at least 1.40, or at least 1.45, or at least 1.50,or at least 1.55, or at least 1.60, or at least 1.65, or at least 1.70,or at least 1.75, or at least 1.80, or at least 1.90, and/or 6.0 orless, or 5.0 or less, or 4.0 or less.

In addition to the above molecular weight quantities, GPC can also beused to quantitatively distinguish a high viscosity base stock fromconventional Group I, Group II, and/or Group III base stocks based onthe elution time of various components within a sample. The elution timein GPC is inversely proportional to molecular weight, so the presence ofpeaks at earlier times demonstrates the presence of heavier compoundswithin a sample. For a conventional base stock formed from a mineralpetroleum feed, less than 0.5 wt % of the conventional base stock willelute prior to 23 minutes, which corresponds to a number averagemolecular weight (M_(n)) of about 3000 g/mol. This reflects the natureof a mineral petroleum sample, which typically contains little or nomaterial having a molecular weight greater than 3000 g/mol. By contrast,the high viscosity base stocks described herein can include substantialamounts of material having a molecular weight (M_(n)) greater than 3000g/mol, such as a high viscosity base stock having at least about 5 wt %of compounds with a molecular weight greater than 3000 g/mol, or atleast about 10 wt %, or at least about 20 wt %, or at least about 30 wt%.

Another characterization method that can provide insight intocompositional differences is Quantitative ¹³C-NMR. Using ¹³C-NMR, thenumber of epsilon carbons present within a sample can be determinedbased on characteristic peaks at 29-31 ppm. Epsilon carbons refer tocarbons that are at least 5 carbons away from a branch (and/or afunctional group) in a hydrocarbon. Thus, the amount of epsilon carbonsis an indication of how much of a composition corresponds to wax-likecompounds. For a Group I base stock formed by conventional methods, theamount of epsilon carbons can be at least about 25 wt % to 27 wt %. Thisreflects the fact that typical Group I base stock, particularly a basestock formed by solvent processing, includes a high proportion ofwax-like compounds. By contrast, a high viscosity base stock asdescribed herein can have a epsilon carbon content of 23.5 wt % or less,or 23.0 wt % or less, or 22.5 wt % or less, or 22.0 wt % or less, or21.5 wt % or less. The reduced amount of epsilon carbons is unexpectedgiven the coupling reactions used to form larger compounds for a highviscosity base stock. Without being bound by any particular theory, itis believed that the unexpectedly low epsilon carbon content of a highviscosity base stock can contribute to unexpectedly beneficial lowtemperature properties, such as pour point, cloud point, and lowtemperature viscosity.

An example of an unexpectedly beneficial low temperature property can bethe crystallization temperature for a high viscosity base stock.Conventional Group I bright stocks can have crystallization temperaturesbetween 0° C. and −10° C., which can pose difficulties with use incertain environments. By contrast, the high viscosity base stocksdescribed herein can have a crystallization temperature of −25° C. orless, or −30° C. or less, or −35° C. or less, or −40° C. or less, or−50° C. or less.

Additionally or alternately, the high viscosity base stocks describedherein can have favorable glass transition temperatures relative to aconventional high viscosity base stock. The high viscosity base stocksdescribed herein can have a glass transition temperature of −40° C. orless, or −50° C. or less, or −60° C. or less.

Although the composition of a high viscosity base stock as describedherein is clearly different from a conventional Group I base stock, someproperties of the high viscosity base stock can remain similar to and/orcomparable to a conventional Group I base stock. The density at 15.6° C.of a high viscosity base stock can be, for example, 0.87 g/cm³ to 0.93g/cm³, which is similar to the density for a conventional Group I brightstock. For example, the density can be 0.87 g/cm³ to 0.93 g/cm³, or 0.87g/cm³ to 0.92 g/cm³, or 0.88 g/cm³ to 0.93 g/cm³ or 0.88 g/cm³ to 0.92g/cm³, or 0.89 g/cm³ to 0.93 g/cm³, or 0.89 g/cm³ to 0.92 g/cm³.

Another option for characterizing a high viscosity base stock asdescribed herein relative to a conventional base stock is based onviscosity and/or viscosity index. With regard to viscosity, a convenientvalue for comparison can be kinematic viscosity at 40° C. or at 100° C.For a conventional Group I base stock, a kinematic viscosity at 40° C.of 460 cSt is desirable for meeting various specifications. Typicalvalues for kinematic viscosity at 40° C. for Group I bright stocks cantypically be near 460 cSt. By contrast, high viscosity base stocks asdescribed herein can have kinematic viscosities at 40° C. of at least600 cSt, or at least 650 cSt, or at least 700 cSt, or at least 800 cSt,or at least 1000 cSt, such as up to 6000 cSt or more. Additionally oralternately, the high viscosity base stocks described herein can havekinematic viscosities at 100° C. of at least 35 cSt, or at least 40 cSt,or at least 50 cSt, or at least 60 cSt, or at least 70 cSt, or at least85 cSt, or at least 100 cSt, such as up to 1000 cSt or more.

The viscosity index of a high viscosity base stock can also be suitablefor use of the high viscosity base stock as a Group I base stock and/orcan be higher than the viscosity index range for a Group I base stock.In various aspects, the viscosity index of a high viscosity base stockcan be 80 to 150, or 80 to 135, or 80 to 120, or 90 to 150, or 90 to135, or 90 to 120, or 100 to 150, or 100 to 135, or 100 to 120.

Additionally or alternately, a high viscosity base stock can also have adesirable pour point. In various aspects, the pour point of a highviscosity base stock can be 0° C. or less, or −5° C. or less, or −10° C.or less, or −15° C. or less, or −20° C. or less, and/or down to anyconvenient low pour point value, such as −60° C. or even lower.

The sulfur and aromatic content of a high viscosity base stock can alsobe comparable to and/or improved relative to typical values for a GroupI base stock or bright stock. For a conventional bright stock,hydroprocessing is not typically performed on the feed during processingbecause hydroprocessing of sufficient severity to remove sulfur and/orreduce aromatics can also substantially reduce the viscosity of theresulting base stock product. By contrast, the high viscosity basestocks described herein can actually benefit from hydroprocessing(and/or other catalytic processing) of various types. As a result,control of the sulfur content and/or aromatics content of high viscositybase stocks can be provided by selecting appropriate catalyticprocessing conditions. In various aspects, the sulfur content of a highviscosity base stock can be 1.0 wt % or less, or 0.75 wt % or less, or0.5 wt % or less, or 0.4 wt % or less, or 0.3 wt % or less, or 0.1 wt %or less, or 0.05 wt % or less, and/or at least 0.01 wt %, or at least0.03 wt %. With regard to aromatics, the total aromatics in a highviscosity base stock can be about 30 wt % or less, or about 20 wt % orless, or about 15 wt % or less, or about 10 wt % or less, or about 8 wt% or less, and/or at least about 1 wt %, or at least about 3 wt %, or atleast about 5 wt %.

Another way to characterize aromatic content can be based on therelative amount of polynuclear aromatics present in a sample. Onepotential concern for a base stock formed via coupling reactions can bethat the number of polynuclear aromatic cores might be increased. Thiscan be characterized based on UV absorptivity at various wavelengths.The UV absorption at 226 nm roughly corresponds to a total aromaticsamount while absorption at 302 nm is indicative of polynuclear aromaticcores. In various aspects, the ratio of UV absorptivity at 302 nm versusUV absorptivity at 226 nm can be 0.20 or less, or 0.18 or less, or 0.16or less.

Examples of Characterization of High Viscosity Base Stocks

In Examples 1-4 below, a hydrocarbon feed corresponding to a Core 100Group I base stock was placed in a glass round-bottom flask equippedwith a distillation condenser. Additional details regarding the reactionconditions and products from Examples 1-4 are shown in FIG. 9. The feedwas first purged with nitrogen and then heated to 150° C. The radicalinitiator di-tert-butyl peroxide (DTBP, 10-60 wt % relative to weight ofbase stock in the feed) was added slowly using a syringe pump over aperiod of 1-4 hours. The decomposition products of DTBP, tert-butanol(major) and acetone (minor), were continuously removed from the reactionmixture by distillation. After completing the addition of DTBP, thereaction mixture was maintained at 150° C. for additional 1-2 hours andthen raised to 185° C. for another 1-2 hours. The excess and unreactedfeed was first removed from the reaction mixture by vacuum distillation(<0.1 mm Hg or <0.013 kPa, 200° C.). For Examples 2-4, the remainingmaterial was then hydro-finished over a Pd/C catalyst, at 150° C.-200°C. under 500 psig-1000 psig (3.4-6.9 MPag) of hydrogen to yield thefinal product.

Performing a coupling reaction on a feed corresponding to a Group I basestock and/or a feed suitable for formation of Group I base stocks canproduce a product having components of higher molecular weight than alubricant base stock produced by conventional solvent processing and/orcatalytic hydroprocessing. The higher molecular weight product can alsohave several properties not observed in conventional lubricant base oilproducts. Without being bound by any particular theory, it is believedthat the unusual compositional properties of the high viscosity basestock are related to the ability of the high viscosity base stock tohave a high molecular weight while retaining other base stock propertiesthat are usually associated with lower molecular weight compounds.

Table 1 shows various molecular weight related properties for severalbasestocks. The first row shows properties for Core 2500 (available fromExxonMobil Corporation), which is a conventional Group I Bright Stockformed by solvent processing. The second row shows properties forSpectraSyn™ 40, a polyalphaolefin base stock formed by oligomerizationof C₈ to C₁₂ alpha olefins that is available from ExxonMobilCorporation. Examples 1-4 represent base stocks formed by coupling of a4 cSt conventional Group I base stock. Example 1 corresponds to a samplethat was not hydroprocessed after coupling of the 4 cSt Group I basestock feed. Examples 2-4 are samples of high viscosity basestock asdescribed herein that were hydroprocessed after the coupling reaction.As shown in Table 1 below, increasing the amount of DTBP relative to theamount of base stock feed resulted in a higher molecular weight product.

TABLE 1 Molecular Weight Properties Wt % Eluted before 23 PD* = min.(>3000 Description Mw* Mn* Mw/Mn Mn) Core 2500, Group I Bright Stock1163 966 1.20 <0.2 SpectraSyn 40, 40 cSt PAO 2768 2188 1.27 35.6 Example1 1283 803 1.60 4.7 Example 2 2240 1146 1.95 24.1 Example 3 2123 12081.76 20.4 Example 4 6239 1887 3.31 56.5

For each composition, Table 1 shows the weight average molecular weight,number average molecular weight, polydispersity, and the weightpercentage of the composition having a molecular weight greater than3000 mol/g, as determined based on Gel Permeation Chromatography. Thedefinitions for M_(w), M_(n), and polydispersity are provided above. Themolecular weights of the samples were analyzed by Gel PermeationChromatography (GPC) under ambient condition using a Waters Alliance2690 HPLC instrument fitted with three 300 mm×7.5 mm 5 um PLgel Mixed-Dcolumns supplied by Agilent Technologies. The samples were first dilutedwith tetrahydrofuran (THF) to −0.6 w/v % solutions. A 100 uL of thesample solution was then injected onto the columns and eluted withun-inhibited tetrahydrofuran (THF) purchased from Sigma-Aldrich at 1mL/min flow rate. Two detectors were used, corresponding to a Waters2410 Refractive Index and a Waters 486 tunable UV detector @ 254 nmwavelength.

As shown in Table 1, the high viscosity base stocks of Examples 2-4 havemolecular weights (M_(w) or M_(n)) that are comparable to orsignificantly greater than the molecular weight of the polyalphaolefinbase stock. By contrast, the base stock of Example 1 has a molecularweight similar to a conventional Group I base stock.

Table 1 also shows the polydispersity for the samples. As shown in Table1, Examples 2-4 have a polydispersity of greater than 1.75, whichindicates an unusually large amount of variation of molecular weightswithin the sample. By contrast, the conventionally formed Group I brightstock and the polyalphaolefin base stock have polydispersity valuesbelow 1.3. It is noted that although Example 1 has apparentlyconventional Group I base stock values for M_(w) and M_(n), thepolydispersity for Example 1 of 1.60 is closer to the polydispersityvalues of Examples 2-4 than to the polydispersity values for either theconventional Group I bright stock or the polyalphaolefin.

The final column in Table 1 shows the weight percent of each sample thateluted prior to 23 minutes (corresponding to 3000 g/mol) during the GelPermeation Chromatography (GPC) characterization. As noted above, theelution time in GPC is inversely proportional to molecular weight, sothe presence of peaks prior to 23 minutes demonstrates the presence ofheavier compounds within a sample. The presence of peaks prior to 23minutes by GPC was selected as a characteristic due to the fact thatconventional mineral petroleum sources do not typically containcompounds of this molecular weight. This is shown for the conventionalGroup I base stock in Table 1, where the weight percent that elutesbefore 23 minutes is less than 0.2 wt %. This clearly shows the contrastbetween a conventional Group I base stock and the high viscosity basestocks described herein, as compounds are present within the highviscosity base stocks that are simply not present within a conventionalGroup I base stock. Further details regarding the GPC characterizationof each sample are shown in FIG. 8, which shows the fullcharacterization results.

As shown in Table 1 and FIG. 8, performing a coupling reaction using aGroup I base stock as a feed can generate compositions with unusualmolecular weight profiles. The novelty of these high viscositycompositions can be further understood based on the properties of thecompositions. FIG. 9 shows a variety of physical and chemical propertiesfor the high viscosity base stocks from Examples 1-4 in comparison withthe conventional CORE 2500 Group I bright stock.

In FIG. 9, the first two properties shown correspond to kinematicviscosity at 40° C. and 100° C. The viscosity values for theconventional Group I base stock are representative of expected valuesfor a bright stock formed by solvent processing. Example 1 which was nothydroprocessed has kinematic viscosities that are somewhat higher butcomparable to a conventional Group I bright stock. By contrast, Examples3 and 4 show substantially increased kinematic viscosities, withkinematic viscosities at 100° C. of greater than 100 cSt and greaterthan 3000 at 40° C.

Although Examples 3 and 4 have unexpectedly high viscosities, theviscosity index of the high viscosity base stocks in Examples 2-4 isalso favorable relative to a conventional base stock. Examples 2 and 3both have viscosity index values greater than 100, while Example 4 has aviscosity index value that could actually correspond to a Group IIIbright stock if the sulfur content was lower. It is noted that eventhough Example 1 was not hydroprocessed, the viscosity index is stillsufficiently high for Example 1 to correspond to a Group I bright stock.

The next property in FIG. 9 is density. Conventionally, the density ofan oligomerized base stock might be expected to increase relative to thedensity of the individual compounds used to form the oligomer. Incontrast, the formation of high molecular weight compounds in the basestocks in Examples 2-4 has not resulted in a substantial densityincrease. Instead, the density of the high viscosity base stocks inExamples 2-4 is comparable to the density of the conventional Group Ibase stock. (Example 2 actually has a lower density than the comparativeGroup I bright stock.) Lower densities are desirable for base stocks aslower density usually correlates with improved energy efficiency.

The high viscosity base stocks in Examples 2-4 can also have a favorablesulfur content relative to a conventional bright stock. The conventionalGroup I base stock in FIG. 9 has a typical sulfur value for a brightstock of about 1 wt % (determined according to ASTM D2622-1). Bycontrast, the high viscosity base stocks in Examples 2-4 actuallybenefit from hydroprocessing. This can allow reduction of sulfur to adesired level. This reduced level of sulfur can be beneficial, as atleast some lubricant formulations are sensitive to sulfur level.

The high viscosity base stocks described herein can also becharacterized based on aniline point. As shown for Examples 2-4, thehydroprocessing of the high viscosity base stock resulted in a productwith a higher aniline point than a conventional Group I bright stock.Examples 2-4 each have an aniline point of at least 125° C. (determinedaccording to ASTM D611).

The next two properties in FIG. 9 are glass transition temperature andcrystallization temperature, as determined using differential scanningcalorimetry. The glass transition temperature of the high viscosity basestocks described herein is comparable to the glass transitiontemperature for a conventional Group I bright stock. However, thecrystallization temperature for the high viscosity base stocks isunexpectedly superior to a conventional Group I bright stock. As shownin FIG. 9, the conventional Group I bright stock has a crystallizationtemperature between 0° C. and −10° C. By contrast, the high viscositybase stocks of Examples 2-4 having crystallization temperatures of −35°C. or lower. This is a substantial improvement in cold flow properties,and indicates that the high viscosity base stocks can have superiorvalues for properties such as pour point and/or cloud point. Theimproved cold flow properties are particularly unexpected in view of thesubstantially higher viscosities of Examples 3 and 4.

The final two properties in FIG. 9 are properties determined by ¹³C-NMR.One property is the percentage of epsilon carbons in the sample, whichcorresponds to a characteristic peak at 29-31 ppm. Epsilon carbons arecarbons that are 5 carbons removed from a branch (and/or a functionalgroup) in a hydrocarbon or hydrocarbon-like compound. Such epsiloncarbons are indicative of the presence of long waxy chains within asample. Although long waxy chains are commonly present in conventionallubricant base stocks, increased amounts of such long waxy chainstypically correlate with less favorable values in cold flow propertiessuch as pour point or cloud point. The conventional Group I bright stockin Table 2 has a typical value for epsilon carbons of about 27 wt %.Although the molecular weights of the samples in Examples 2-4 aresubstantially higher, the percentage of epsilon carbons is less than 22wt % for all of the samples. The non-hydroprocessed sample of Example 1also has an epsilon carbon amount of less than 22 wt %.

The ¹³C-NMR can also be used to determine the amount of aromatic carbonsin a sample, based on peaks between 117 ppm and 150 ppm. In spite ofhydroprocessing, the amount of aromatic carbons in Examples 2 and 3 isactually greater than the amount of aromatics in the conventional GroupI bright stock.

One potential concern for a base stock formed via coupling reactions canbe that the number of polynuclear aromatic cores might be increased.However, the high viscosity base stocks in Examples 1 to 4 show noincrease in the amount of polynuclear aromatic cores relative to aconventional Group I bright stock. FIG. 10 shows a comparison of the UVasbsorptivity of the conventional Group I bright stock and Examples 1 to4 at various wavelengths. The UV absorption at 226 nm roughlycorresponds to a total aromatics amount while 302 nm is indicative ofpolynuclear aromatic cores. As shown in FIG. 10, the ratio of PNAs tototal aromatics for the high viscosity base stocks is comparable to thevalue for the conventional Group I bright stock.

Example 5: Lubricant Formulation—Gear Oil Properties

In addition to the above physical and chemical properties, highviscosity base stocks can provide other types of improved properties. Inthis Example, the high viscosity base stock corresponding to Example 3was used to formulate an ISO VG 220 gear oil. An ISO VG 220 gear oil wasalso formulated using the conventional CORE 2500 Group I bright stock.The same amount of the same additive package and the same rebalancinglight neutral base stock were used for both gear oils to make therequired viscosity grade. Two formulation performance features weremeasured. One measured feature was low temperature properties using ASTMtest method D2983, Brookfield viscosity at −20° C. A second measuredfeature was oxidation stability using US Steel S-200 at 121° C. for 13days.

FIG. 11 shows a comparison of the Brookfield viscosity at −20° C. forthe gear oil formulated using the conventional Group I bright stock andthe gear oil formulated using the high viscosity base stock of Example3. As shown in FIG. 11, the gear oil formulated using Example 3 has aBrookfield viscosity of less than 100,000, while the gear oil formulatedusing the conventional bright stock has a substantially higherviscosity. As shown in Table 2, it is noted that the crystallizationtemperature of the conventional bright stock is higher than −20° C.,which likely contributes to the high viscosity. The lowercrystallization temperature of the high viscosity base stock of Example3 allows the formulated gear oil to retain a desirable viscosity at lowtemperatures.

FIG. 12 shows results from performing the US Steel oxidation test on thegear oils formulated using the conventional bright stock and the highviscosity base stock of Example 3, respectively. Conventionally, a gearoil formulated using a higher molecular weight base stock would beexpected to perform less favorably under this severe oxidation test.However, in spite of the substantially higher molecular weight, the gearoil formulated using the high viscosity base stock of Example 3 had acomparable degree of oxidation (similar to within the experimental errorof the method) to the gear oil formulated using the conventional brightstock.

Example 6: Lubricant Formulation—Gear Oil Properties

In this Example, the high viscosity base stock corresponding to Example3 was used to formulate an ISO VG 220 gear oil. A second ISO VG 220 gearoil was also formulated using the conventional CORE 2500 Group I brightstock. The same amount of the same additive package and the samerebalancing light neutral base stock were used for the formulated gearoils to make the required viscosity grade. Two formulation performancefeatures were measured. One measured feature was low temperatureproperties using ASTM test method D2983, Brookfield viscosity at −35° C.A second measured feature was oxidation stability using ASTM test methodD2272, the Rotating Pressure Vessel Oxidation Test (RPVOT) at 150° C.

FIG. 13 shows a comparison of the Brookfield viscosity at −35° C. forthe gear oil formulated using the conventional Group I bright stock, thegear oil formulated using the high viscosity base stock of Example 3,and a gear oil formulated using a polyalphaolefin (high viscosity GroupIV) base stock. As shown in FIG. 13, the gear oil formulated usingExample 3 has a Brookfield viscosity at −35° C. of about 350,000, whilethe gear oil formulated using the conventional bright stock has aBrookfield viscosity at −35° C. that exceeds the test limit of1,000,000. As in Example 5, formulating a gear oil using the highviscosity base stocks described herein provides superior low temperatureperformance relative to a conventional Group I bright stock. In FIG. 13,it is not surprising that the gear oil formulated using the Group IVbase stock provides a still lower Brookfield viscosity at −35° C.

FIG. 14 shows results from a Rotating Pressure Vessel Oxidation Test(RPVOT), a demanding test for assessing highly stable gear oils, thatwas performed on gear oils formulated using the same types of basestocks as in FIG. 13. In the RPVOT oxidation stability test, the gearoil formulated using the high viscosity base stock of Example 3performed similarly (within experimental error of the test) to the gearoil formulated using the traditional bright stock. This comparableperformance is achieved despite a higher molecular weight, which isconventionally believed to be detrimental to oxidation stability. Asexpected, both of the gear oils formulated using Group I base stocksshow poorer performance compared to the Group IV based formulation.

Additional Embodiments Embodiment 1

A base stock composition having a number average molecular weight(M_(n)) of 600 g/mol to 3000 g/mol, a weight average molecular weight(M_(w)) of 900 g/mol to 10000 g/mol, a polydispersity (M_(w)/M_(n)) ofat least 1.4, a pour point of 0° C. or less, a viscosity at 100° C. ofat least 35 cSt, a viscosity at 40° C. of at least 600 cSt, and aviscosity index of at least 50.

Embodiment 2

The composition of Embodiment 1, wherein the polydispersity is at least1.5, or at least 1.7, or at least 1.9, and optionally less than 5.0, orless than 4.0.

Embodiment 3

The composition of any of the above embodiments, wherein the compositionhas 23.5 wt % or less of epsilon carbons as determined by ¹³C-NMR, or23.0 wt % or less, or 22.5 wt % or less, or 22.0 wt % or less.

Embodiment 4

The composition of any of the above embodiments, wherein the numberaverage molecular weight (M_(n)) is at least 900 g/mol, or at least 1000g/mol; or wherein the weight average molecular weight (M_(w)) is atleast 1200 g/mol, or at least 1500 g/mol, or at least 2000 g/mol; or acombination thereof.

Embodiment 5

The composition of any of the above embodiments, wherein the compositionhas a glass transition temperature of −40° C. or less, or −50° C. orless, or −60° C. or less; or wherein the composition has acrystallization temperature of −20° C. or less, or −30° C. or less, or−40° C. or less; or a combination thereof.

Embodiment 6

The composition of any of the above embodiments, wherein the compositionhas a sulfur content of 0.5 wt % or less, or 0.4 wt % or less.

Embodiment 7

The composition of any of the above embodiments, wherein the compositionhas a) a kinematic viscosity at 40° C. of at least 700 cSt, or at least800 cSt, or at least 1000 cSt; b) a kinematic viscosity at 100° C. of atleast 40 cSt, or at least 50 cSt, or at least 60 cSt, or at least 70cSt; or c) a combination thereof.

Embodiment 8

The composition of any of the above embodiments, wherein the viscosityindex is at least 80, or at least 90, or at least 100, and/or 150 orless, or 135 or less, or 120 or less.

Embodiment 9

The composition of any of the above embodiments, wherein the compositionhas a ratio of UV absorptivity at 302 nm versus UV absorptivity at 226nm of 0.20 or less, or 0.18 or less.

Embodiment 10

A formulated lubricant comprising the base stock composition of any ofthe above embodiments.

Embodiment 11

A method of forming a base stock composition, comprising: introducing afeedstock having a viscosity index of 50 to 120, a viscosity at 100° C.of 12 cSt or less, and at least one of a sulfur content greater than0.03 wt % and an aromatics content greater than 10 wt %, into a couplingreaction stage under effective coupling conditions to form a coupledeffluent; and fractionating at least a portion of the coupled effluentto form at least a first product fraction having a viscosity index of atleast 50, a polydispersity (M_(w)/M_(n)) of at least 1.4, a viscosity at100° C. of at least 35 cSt, a viscosity at 40° C. of at least 600 cSt,and a pour point of 0° C. or less.

Embodiment 12

The method of Embodiment 11, further comprising exposing at least aportion of the coupled effluent to a catalyst under effective catalyticprocessing conditions to form a catalytically processed effluent,wherein fractionating at least a portion of the coupled effluentcomprises fractionating at least a portion of the catalyticallyprocessed effluent.

Embodiment 13

A method of forming a base stock composition, comprising: introducing afeedstock having a viscosity index of 50 to 120, a viscosity at 100° C.of 12 cSt or less, and at least one of a sulfur content greater than0.03 wt % and an aromatics content greater than 10 wt %, into a couplingreaction stage under effective coupling conditions to form a coupledeffluent; fractionating at least a portion of the coupled effluent toform at least a first coupled effluent fraction; and exposing at least aportion of the first coupled effluent fraction to a catalyst undereffective catalytic processing conditions to form the first productfraction having a viscosity index of at least 50, a polydispersity(M_(w)/M_(n)) of at least 1.4, a viscosity at 100° C. of at least 35cSt, a viscosity at 40° C. of at least 600 cSt, and a pour point of 0°C. or less.

Embodiment 14

The method of any of Embodiments 11-13, wherein the effective catalyticprocessing conditions comprises at least one of hydrotreatmentconditions, catalytic dewaxing conditions, and hydrofinishingconditions.

Embodiment 15

The method of any of Embodiments 11-14, wherein the effective couplingconditions comprise exposing the feedstock to at least 20 wt % dialkylperoxide relative to a combined weight of feedstock and peroxide, or atleast 30 wt %, or at least 40 wt %.

Embodiment 16

The method of any of Embodiments 11-14, wherein the effective couplingconditions comprise acid-catalyzed coupling conditions, the acidoptionally comprising a solid acid, preferably a molecular sieve.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.Although the present disclosure has been described in terms of specificembodiments, it is not so limited. Suitable alterations/modificationsfor operation under specific conditions should be apparent to thoseskilled in the art. It is therefore intended that the following claimsbe interpreted as covering all such alterations/modifications as fallwithin the true spirit/scope of the disclosure.

1-13. (canceled)
 14. A method of forming a base stock composition,comprising: introducing a feedstock having a viscosity index of 50 to120, a kinematic viscosity at 100° C. of 12 cSt or less, and at leastone of a sulfur content greater than 0.03 wt % and an aromatics contentgreater than 10 wt %, into a coupling reaction stage under effectivecoupling conditions to form a coupled effluent; and fractionating atleast a portion of the coupled effluent to form at least a first productfraction having a viscosity index of at least 50, a polydispersity(M_(w)/M_(n)) of at least 1.4, a kinematic viscosity at 100° C. of atleast 35 cSt, a kinematic viscosity at 40° C. of at least 600 cSt, and apour point of 0° C. or less.
 15. The method of claim 14, wherein theeffective coupling conditions comprise exposing the feedstock to atleast 20 wt % dialkyl peroxide relative to a combined weight offeedstock and peroxide.
 16. The method of claim 14, wherein theeffective coupling conditions comprise acid-catalyzed couplingconditions.
 17. The method of claim 14, further comprising exposing atleast a portion of the coupled effluent to a catalyst under effectivecatalytic processing conditions to form a catalytically processedeffluent, wherein fractionating at least a portion of the coupledeffluent comprises fractionating at least a portion of the catalyticallyprocessed effluent.
 18. The method of claim 17, wherein the effectivecatalytic processing conditions comprises at least one of hydrotreatmentconditions, catalytic dewaxing conditions, and hydrofinishingconditions.
 19. The method of claim 14, wherein the polydispersity is atleast 1.7.
 20. A method of forming a base stock composition, comprising:introducing a feedstock having a viscosity index of 50 to 120, akinematic viscosity at 100° C. of 12 cSt or less, and at least one of asulfur content greater than 0.03 wt % and an aromatics content greaterthan 10 wt %, into a coupling reaction stage under effective couplingconditions to form a coupled effluent; fractionating at least a portionof the coupled effluent to form at least a first coupled effluentfraction; and exposing at least a portion of the first coupled effluentfraction to a catalyst under effective catalytic processing conditionsto form the first product fraction having a viscosity index of at least50, a polydispersity (M_(w)/M_(n)) of at least 1.4, a kinematicviscosity at 100° C. of at least 35 cSt, a kinematic viscosity at 40° C.of at least 600 cSt, and a pour point of 0° C. or less.